1. Field of the Invention
The present invention relates to a recording tape cartridge which rotatably accommodates a reel onto which recording tape, such as a magnetic tape or the like, is wound.
2. Description of the Related Art
Recording tapes such as magnetic tapes and the like are used as external recording media for computers and the like. “One-reel” recording tape cartridges, which rotatably accommodate a single reel onto which a recording tape is wound in a case, can reduce space for accommodation during storage and can record large amounts of information, and are employed as such recording tapes.
Such a recording tape cartridge is equipped with a brake structure such that the reel does not rotate inside the case at times of non-use (see, for example, the specification of Japanese Patent No. 3,187,022). A recording tape cartridge equipped with this brake structure is now described with reference to FIGS. 13 and 14.
In a recording tape cartridge 200 shown in FIG. 13, a single reel 204 is accommodated in a case 202. The case 202 is formed by joining peripheral walls of a lower case 202A and an upper case 202B to one another. The case 202 is provided with a gear aperture 206 and a rotation-limiting rib 208. The gear aperture 206 is formed at a central portion of a floor plate of the lower case 202A of the case 202. The rotation-limiting rib 208 protrudes downward from a ceiling plate of the upper case 202B of the case 202.
The reel 204 is provided with a reel hub 210, which is formed in the shape of a circular tube with a base, around an outer peripheral portion of which recording tape is wound. At a lower face of a base portion 210A of the reel hub 210, a reel gear 214 is formed in an annular shape. The reel gear 214 is meshable with a driving gear 212A, which is formed at a rotation shaft 212 of a drive device. Insertion through-holes 216, which penetrate through the base portion 210A, are formed at a plurality of locations on a circular periphery, at the portion at which the reel gear 214 is formed. The insertion through-holes 216 are equidistant. A diameter of each insertion through-hole 216 is set to be larger than a gear pitch of the reel gear 214, and teeth of the reel gear 214 are not provided in a vicinity around each insertion through-hole 216.
At an upper face of the base portion 210A of the reel hub 210, engaging protrusions 218 are provided standing from (portions of) a plurality of locations along the predetermined circular periphery, between the insertion through-holes 216. Gear teeth 218A are formed at upper end portions of the engaging protrusions 218.
A disc-like brake member 220 is insertedly provided inside the reel hub 210. At a lower face of the brake member 220, an annular brake gear 220A is provided. The brake gear 220A is meshable with the gear teeth 218A. A projection 222 is provided standing from an upper face of the brake member 220. The projection 222 is provided with an insertion groove 222A, into which the rotation-limiting rib 208 of the case 202 is inserted. When the rotation-limiting rib 208 is entered into the insertion groove 222A, the brake member 220 is rendered incapable of rotating relative to the case 202. Further, the brake member 220 is rendered movable only in a vertical direction, being guided by the rotation-limiting rib 208.
A compression coil spring 224 is disposed between the ceiling plate of the upper case 202B and the brake member 220. Usually, the brake member 220 is urged downward by urging force of the compression coil spring 224, such that the brake gear 220A is meshed with the gear teeth 218A. Therefore, the brake member 220 is usually set to a rotation-locked state in which rotation of the reel 204 relative to the case 202 is blocked. Moreover, the reel 204 is pressed against the floor plate of the lower case 202A by this urging force, and the reel gear 214 is exposed through the gear aperture 206.
A release member 226 is disposed between the base portion 210A of the reel hub 210 and the brake member 220, so as to abut against the base portion 210A and the brake member 220. The release member 226 is formed in a plate form which does not interfere with the engaging protrusions 218, and is provided with leg portions 226A, which are respectively inserted into the insertion through-holes 216.
Thus, when the driving gear 212A is operated to mesh with the reel gear 214, as shown in FIG. 14, the leg portions 226A are pushed by the driving gear 212A, against the urging force of the compression coil spring 224, and the release member 226 is pushed upward. The release member 226 moves away from the base portion 210A and pushes the brake member 220 upward. Thus, meshing between the brake gear 220A and the gear teeth 218A is released. At this time, the reel 204 also rises relative to the floor plate of the lower case 202A, and the reel 204 becomes rotatable inside the case 202.
Hence, the reel 204, whose reel gear 214 meshes with the driving gear 212A of the rotation shaft 212, is a structure which rotates in the case 202 when the rotation shaft 212 rotates. At such a time, the release member 226 rotates with the reel 204, and an axial center portion of the release member 226 rubs against (slidingly contacts) an axial center portion of the brake member 220. Accordingly, the axial center portion of the brake member 220 is formed with a protrusion portion 220B, which is formed substantially in a spherical surface form. Thus, the axial center portion of the brake member 220 is substantially in point contact with the axial center portion of the release member 226.
Later, when the state of meshing of the driving gear 212A with the reel gear 214 is released, the brake member 220 is moved downward by the urging force of the compression coil spring 224, the brake gear 220A meshes with the gear teeth 218A, and the reel 204 is pushed against the floor plate of the lower case 202A. As a result, this structure returns to the rotation-locked state in which rotation of the reel 204 relative to the case 202 is blocked.
When the recording tape cartridge 200 is to be assembled, the reel 204 is placed on the lower case 202A such that a lower end portion of the reel hub 210 enters into the gear aperture 206. Thereafter, the leg portions 226A are respectively inserted into the insertion through-holes 216 and the release member 226 is placed on the base portion 210A of the reel hub 210. Then, the brake member 220 is placed on the engaging protrusions 218 of the reel hub 210 such that the brake gear 220A meshes with the gear teeth 218A. Further, in a state in which the compression coil spring 224 has been placed on the brake member 220, the upper case 202B is moved toward the lower case 202A while the compression coil spring 224 is compressed and the rotation-limiting rib 208 is inserted into the insertion groove 222A of the brake member 220. The peripheral walls of the upper case 202B and the lower case 202A are matched up with one another and, in this state, joined. As a result, rotation of the reel 204 relative to the case 202 in the recording tape cartridge 200 is blocked at a time of shipping, which is a time of non-use.
Further, although this is not shown in the drawings, a structure is also known in which the release member 226 is not provided (see, for example, Japanese Patent Application Laid-Open (JP-A) No. 63-251983). Herein, the protrusion portion 220B of the brake member 220 is directly pushed by a release portion, which is protrudingly provided at an axial center portion of the rotation shaft 212 and advances in through a through-hole which penetrates through the base portion 210A of the reel hub 210. Thus, the brake member 220 is pushed upward, and the rotation-locked state of the reel 204 is released. In a recording tape cartridge of this structure, rather than the engaging protrusions 218 being provided, gear teeth are provided in an annular form at the base portion of the reel hub. Thus, because of the rotation-limiting rib of the case, the brake member provides both functions of blocking rotation and guiding in a direction of moving toward/away from the gear teeth. Consequently, a process of assembling a recording tape cartridge of this structure is essentially similar to the process of assembly of the recording tape cartridge 200 described above, except for steps of assembling the release member 226.
However, with the conventional recording tape cartridge 200 as described above, when the brake member 220 is placed on the engaging protrusions 218 of the reel hub 210, if the axial center of the brake member is offset with respect to the axial center of the reel 204, the brake member 220 may be placed on the engaging protrusions 218 in a state in which tooth peaks of the brake gear 220A ride up on tooth peaks of the gear teeth 218A. In such a case, because a clearance is provided between the insertion groove 222A of the brake member and the rotation-limiting rib 208 of the upper case 202B, the rotation-limiting rib 208 is still inserted into the insertion groove 222A. Consequently, subsequent processes can be executed and the recording tape cartridge 200 assembled, and there is a risk that the recording tape cartridge 200 will be shipped in a state in which rotation of the reel 204 is still enabled. In particular, the problem described above tends to occur in a process of assembly of the recording tape cartridge 200 by manual labor.
As a countermeasure for this problem, the present applicant has previously submitted applications regarding structures provided with a tapering wall which guides the brake member 220 to a position at which the brake gear 220A meshes with the gear teeth 218A during assembly of inserting the brake member 220 into the reel hub 210 (see, for example, Japanese Patent Application No. 2002-276805). In such a structure, the tapering wall guides the brake member 220 in while aligning the brake member 220 with respect to the reel hub 210. As a result, occurrences of the brake member 220 riding up on the gear teeth 218A are greatly suppressed.
However, limiting or preventing the gear teeth of the brake member from riding up during assembly of the braking member by means of a structure different from the invention relating to Japanese Patent Application No. 2002-276805 has also been considered.